Outboard Carb problems

[Jobs a good un]

Morning All

Having problems with my 6hp Tohatsu outboard 2018 , it keeps cutting out after making the revs higher .
It feels like blocked jets in the carb , does anyone know any engineers close to Bristol that could fix it ?
Read somewhere it may need Ultra Sonic blasting ?
Or is the best option just to buy a new carb ?

Thanks

 

[wallacebob]

Get carb cleaner from Halfords, take carb off, spray thro’ jets; simple job. Better to disassemble to do the job thoroughly. If there are deposits in bowl, it probably caused by ethanol fuel. Treat you fuel tank to additive (Halfords or garden centre) a quick search on here will give lots of advice.

 

[Stemar]

My first try would be to take the carb apart - lots of photos to help getting it back together, and before removing any adjustment screws, screw them in all the way, making a note of how many turns, so you can get them back in the same place. Then soak it overnight in carb cleaner.

One other thought. I had a Tohatsu 3.5 with all the symptoms of fuel starvation, but it turned out to be electrical - a bad contact where the coil's earth wire was attached to the block.

Good luck

 

[Bobc]

Replace the float needle. It is probably sticking.

 

[Graham376]

You don't say how soon it cuts out after using high revs, does it immediately cut when you open up or, after an interval? If using remote tank, check the internal filter not partly blocked and try running it with the cap off. 2018 engine had IIRC a 5 year warranty so you may be covered for any replacement parts needed.

 

[Jobs a good un]

You don't say how soon it cuts out after using high revs, does it immediately cut when you open up or, after an interval? If using remote tank, check the internal filter not partly blocked and try running it with the cap off. 2018 engine had IIRC a 5 year warranty so you may be covered for any replacement parts needed.

Hi it starts up fine but as you try to rev it , there is a stutter , will run for 10 mins under load? Then cut out ?

 

[Jobs a good un]

Replace the float needle. It is probably sticking.

Where is the float needle ?

 

[Sealong]

This is very likely to be caused by the ethanol content in modern gasoline which deposits a residue inside the carburettor. For small engines, and therefore small carburettors with small diameter jets this causes blockages. I have an outboard motor and also a vintage motorcycle and it is a constant problem. The only successful solution is to buy yourself an ultrasonic bath, which do not "blast" but gently agitate. They are quite inexpensive (circa £40), and in relation to the time you will otherwise spend without one in cleaning, assembling and then testing it is a bargain. Use the bespoke carburettor cleaning fluid and de-ionised water and make sure the physical size of the bath is sufficiently large enough for your carburettor. I generally find that about five to ten hours is enough to clean all the residue out of the carburettor.

Then for next year, only use premium grade gasoline, which has 5% ethanol, rather than the cheaper grade of fuel which has 10%.

 

[C08]

I needed a new carb on my 20hp Tohatsu at 7 years. It had white calcium like hard deposits that the main dealer did not think would shift even with an us clean. He said he had seen this before and failed to shift it several times quite different to normal gumming up.
I had corrosion of the float needle on a 3.5 Tohatsu and a new needle assembly fixed that.
Your first step is take off the float chamber and see what is in there - new pattern carbs are not expensive and seem good quality.

 

[Refueler]

General post ..... not only Outboard

Depends on the carb ... if its float and needle type - then follow Stemar's advice - but use hot water ... literally as hot as your hands can stand ...... swish the parts about ..... then remove - shake of excess water ... the heat of the bodies will then usually dry them ... re-assemble and test.
If its a Diaphragm carb - then make sure diaphragm is carefully removed before washing .... in many cases - its good to replace the diaphragm ...

Just to correct misrepresentation ........... Regular Gasoline is UP TO 10% but more than 5%, Premium is 0 - 5% Ethanol. There are other grades with up to 85% Ethanol and other Bio's .... but you will not usually see these as they are only sold in specialist outlets,.

 

[Refueler]

OK ... just to post about Ethanol ...

I have a varied assortment of Outboards ranging from 2hp to 35hp ..... we have had Ethanol Gasoline here in Latvia for significant time .... 5 then10%.

I run all my O/bds on regular Gasoline with up to 10% Ethanol.

Only occasionally do I have to clear a carb ... and that's usually through some other reason. I ALWAYS stop my O/bds by shutting of the fuel if they are going to be standing for more than half day ..... if a short stop - then I use the Stop button.
If I stop any by the button and they stand for a day or so - then I have harder job starting them. I can leave my O/bds all winter after fuel shut-off .... get out in spring and I expect to have quite a few pulls to get them going again ... rarely but sometimes a shot of Easy Start just to get them to fire up ..... Once started and given a few minutes - they clear and run fine.

 

[peteK]

Have you tried a new spark plug?

 

[Steve65]

It needs adjusting, its factory set to unworkable settings to pass EPA tests. There is a slow mixture screw. It will have a D shaped head or even an anti tamper plug. Needs turning out a turn

 

[Stingo]

What @Steve65 says, but start with a 1/4 turn, see how it goes, then another 1/4 turn.... and so on.

IIRC, 1 full turn is what you'll eventually need, but that recollection is from about seven years ago, so definitely unreliable

EDIT. It's probably safer to ignore what I've suggested and rather go with Steve65's suggestion

 

[Refueler]

Just to add to my Post #11 .....

Even before the use of Ethanol - I always turned of the fuel to stop the O/bd ..... but if I didn't and left O/bd for a day or so - I has SAME difficulty starting as todays fuel.

On 2str premix engines ... the biggest factor is the 2T oil when the gasoline itself starts vaporise off ... the ignition point of the fuel rises sharply ... jets start getting blocked .... fuel is heavier and not drawn so easily from the float chamber ... Doesn't take a Rocket Scientist to work that out ...
Anyone who's dismantled a carb after its had 2str fuel sit in it will see the residues.

 

[Spirit (of Glenans)]

Where is the float needle ?

When you remove the float chamber the float needle will drop out of a recess in the upper part of the carb body. It looks like a miniature pencil stub made of plastic. Its pointed head engages in an aperture from which the petrol flows to fill the chamber. When the chamber is full the float rises and the needle closes off any further supply until the level in the chamber drops, due to being drawn off through the jets.

 

[Spirit (of Glenans)]

I needed a new carb on my 20hp Tohatsu at 7 years. It had white calcium like hard deposits that the main dealer did not think would shift even with an us clean. He said he had seen this before and failed to shift it several times quite different to normal gumming up.
I had corrosion of the float needle on a 3.5 Tohatsu and a new needle assembly fixed that.
Your first step is take off the float chamber and see what is in there - new pattern carbs are not expensive and seem good quality.

"Pattern carbs", for the uninitated, are unbranded copies bought (usually) off the internet. They are available for all kinds of small petrol engines and are usually reliable, and much less expensive than branded replacements from the original engine manufacturers (who just buy them in anyway)

 

[PetiteFleur]

I had a similar problem with all my small petrol engines, 4T and 2T engines. It was bad fuel - so I only use E5 petrol with an additive. - I use the Honda additive. The old fuel did not smell at all whereas the E5 really smelt strong.

 

[gordmac]

I have had success leaving a complete carb soaking in petrol overnight.

 

[James_Calvert]

If you can, try connecting up to a different fuel tank, and different hose.

I had a similar sounding problem and it turned out that the internals of the hose were getting bunged up. I think it was from a deposit building up inside the hose itself, which I found when trying to replace the priming bulb.

Not a Tohatsu, a 2 stroke 2 cylinder Mercury 6 hp.